Berry Images of Comet 1996 B2 Hyakutake

Sequence of 16 images
taken March 25 UT, with a time resolution of about 15 minutes.
These images are highly processed to reveal low-contrast
features in the tail of the comet.

I shot a 60-second integration every 80 seconds using
Cookbook 245 CCD on a 6"f/5, 4"f/5, or 200mm lens. I grouped the images
and registered them on the comet nucleus. I then
created an image from the median of these frames, which largely eliminates
the "moving" stars. I then used the following process:
CB245 script language: RANK 20 .8 / RANK 12 .5 / GUMA 24 1.6.
This enhances low-contrast features and ignores the elliptical brightness
contour that dominates the raw data.

The rank process compares the brightness of a pixel with its neighbors inside
a given radius. In square of radius 10, there are 441 pixels. Sort the pixels
in the region into ascending order of brightness. If the pixel at the center
is the 235th in brightness rank, it is assigned a value of (235/441)*4095.

The "gain" of the rank process becomes higher the more uniform
the region is. It best detects features roughly equal in dimension to the
radius. It is insensitive to large brightness differences.

To get higher time resolution, I registered all frames on the nucleus and
then created a median image. I used the rank minimum function to erode
details in the median image and then smoothed it with a 24-sigma Gausssian
and then subtracted this from each of the data frames. This removed the
gross brightness contour of the comet. I then stretched the difference, ran
a big Gaussian mask over it, and saved it.